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Lethal High Temperature Extremes of the BrownMarmorated Stink Bug (Hemiptera: Pentatomidae)and Efficacy of Commercial Heat Treatments forControl in Export Shipping CargoAuthor(s): J. D. Aigner and T. P. KuharSource: Journal of Agricultural and Urban Entomology, 32(1):1-6.Published By: South Carolina Entomological SocietyDOI: http://dx.doi.org/10.3954/1523-5475-32.1.1URL: http://www.bioone.org/doi/full/10.3954/1523-5475-32.1.1

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N O T E

Lethal High Temperature Extremes of the BrownMarmorated Stink Bug (Hemiptera: Pentatomidae) andEfficacy of Commercial Heat Treatments for Control in

Export Shipping Cargo1

J. D. Aigner2 and T. P. Kuhar2,3

J. Agric. Urban Entomol. 32: 1–6 (2016)

Since its accidental introduction into the U.S.A. in the mid-1990s, the brownmarmorated stink bug, Halyomorpha halys Stal (Hemiptera: Pentatomidae), hasspread rapidly across North America and become an economically significant pestof tree fruits, vegetables, tree nuts, and field crops (Leskey et al. 2012, Rice et al.2014). Consequently, there has been tremendous interest in better understandingaspects of its biology. Knowledge on the effects of temperature on the bug’sbiology is critical to developing ecological models (Nielsen et al. 2008), predictingrange expansion (Zhu et al. 2012), and for potentially developing pest controltactics using controlled temperature (Hammond 2015). In two laboratoryexperiments, we determine the lethal high temperature extremes of H. halysand efficacy of commercial heat treatments for control of the bug in exportshipping cargo.

Experiments were conducted in 2014 and 2015 in a laboratory at Virginia Techin Blacksburg, VA to determine the lethal high temperature of the brownmarmorated stink bug. All insects used in experiments were obtained froma laboratory colony maintained in mesh cages (30.48 cm 3 30.48 cm 3 30.48 cm)(BioQuip, Rancho Dominquez, CA) at 23uC, 12-h photoperiod, and 50% relativehumidity. Bugs were fed fresh seeds from green beans, Phaseolus vulgarisL. (Fabaceae), and sunflower, Helianthus annuus L. (Asteraceae), and they weresupplied with water through a wick. The colony was continuously supplementedwith field-collected H. halys from trees and crops in Virginia during the summermonths or from manmade structures in the fall and winter of each year. Adults ofboth sexes were haphazardly selected from the colony and placed in groups of tenin 9-cm glass Petri dishes (Corning, Inc., Corning, NY). These groups of bugswere placed in an incubator (Fisher Scientific Thermo Incubator 537D, FisherScientific, Waltham, MA) at different temperature-time intervals. Bugs wereexposed for 4 h at the following temperatures: 35, 38, 40, 42, and 45uC.Additionally, bugs were exposed for 15-min and 1-h intervals at 40, 45, and 50uC.Mortality was assessed at 1 h and 24 h after exposure. Bugs unable to walk

1Accepted for publication 8 December 2015.2Virginia Polytechnic Institute and State University, Department of Entomology, Blacksburg, Virginia

24061 U.S.A.3Corresponding author: tkuhar@vt.edu

1

properly and right themselves after being turned over on their backs wereconsidered lethally injured from the heat exposure and were recorded as dead.Each time and temperature combination was replicated at least four times.Percentage mortality at 24 h after exposure were analyzed using analysis ofvariance (ANOVA) (JMP version 10.0; SAS Institute 2012). Means were separatedusing Fisher’s Protected Least Significant Difference (LSD) at a 5 0.05.

Temperature had a significant effect on bug mortality for the 15-min (F 5

10.88; df 5 2, 9; P , 0.004), 1-h (F 5 80,000; df 5 2, 9; P , 0.0001), and 4-hexposure times (F 5 50.57; df 5 4, 25; P , 0.0001). All H. halys adults that wereexposed to 50uC for $15 min or to 45uC for $1 h were killed (Table 1). TheH. halys adults exposed to 35u, 38u, 40u, 42u, and 45uC for 4 h had an observedmean mortality of 5, 12, 38, 91, and 100%, respectively. Mortality at 42 and 45uCwas significantly higher than it was at the other temperatures, and mortality at40uC was higher than it was at either 38uC or 35uC.

A second study was conducted to evaluate the potential of heat treatmentsfor control of live H. halys in export cargo. In 2015, a heat-treatment facility atthe Port of Savannah, GA, USA was constructed by Willenius WilhelmsenLogistics (WWL, Lysaker, Norway) to create a usable heated space approxi-mately 6.1 m 3 12.2 m 3 3 m (Figure 1a). The interior of the facility was coatedwith a series of spray foam insulation and 5-cm wide foam board insulation toreduce heat loss. One end of the facility allowed for vehicles to enter througha standard exterior grade metal garage door, while the opposite end housedthree 500,000 BTU propane heaters (PEST-HEAT, Aston, PA) (Figure 1b) thatallowed the heat to move throughout the space. These heaters were supplied bya 3785-liter propane tank located in the rear of the facility. Current capabilitiesof this space allow for treatment of up to four standard-sized passenger vehiclesat one time.

For our studies at the Port of Savannah, H. halys field mortality was assessedusing a seven-passenger 2003 Chevrolet Astro Extended Wagon. This vehicle hada 4.6-L V6 CPI engine. The same vehicle was used for all experiments. Previous

Table 1. Average mortality of H. halys adults following exposure fordifferent times and temperatures in an incubator located atVirginia Tech, Blacksburg, VA.

% mortality (mean 6 SE)a

Temp. (uC) 15-min exposureb 1-h exposureb 4-h exposureb

35 – – 5.0 6 1.4 c38 – – 11.7 6 1.9 c40 0.0 6 0.0 b 0.0 6 0.0 b 38.3 6 3.7 b42 – – 91.3 6 2.2 a45 22.5 6 19.3 b 100.0 6 0.0 a 100.0 6 0.0 a50 100.0 6 0.0 a 100.0 6 0.0 a –

aThere were four replications, and more than 50 bugs per temperature-time treatment.bMeans within columns followed by the same letter are not significantly different (ANOVA, LSD test, a 5

0.05).

2 J. Agric. Urban Entomol. Vol. 32 (2016)

testing by WWL identified the engine compartment, under the driver orpassenger seats and interior areas that house the spare tire to be the coldestspots during the heat treatment. The test vehicle did not have an interior sparetire compartment; therefore, we were only able to test for bug survival in theengine compartment and under the seat.

The vehicle was parked in the heat treatment facility and subjected totargeted heat treatments of 40u, 50u, and 60uC. Ten adults (collected nearSharpsburg, MD the week prior to testing) were placed in 1-liter mesh bags(Figure 2) and then placed in the engine compartment and under the driver’s seatfor 15 min once the minimum temperatures in these areas reached the targettemperatures. After reaching the minimum target, temperatures were monitoredat each location every 60 s for 15 min using a hard-wired thermocouple integratedto a BlueTherm Duo system (Thermoworks, Lindon, UT) integrated with theBlueTherm Pro software (Thermoworks, Lindon, UT) for tablets. Stink bugs wereremoved and assessed for mortality at 0, 1, and 24 h after the heat treatment.Each temperature treatment was replicated eight times and each replication hada control group of ten H. halys that were held at ambient temperature witha mean of 16uC. As with the previous experiment, percentage mortality at 24 hafter exposure were analyzed using ANOVA (JMP version 10.0; SAS Institute2012) and means were separated using Fisher’s Protected LSD.

In the second study, temperatures recorded from under the driver’s seat wereabout 2 to 3uC cooler than those recorded in the engine compartment, but bothwere at least at the minimal targeted temperature generated from the heattreatment (Table 2). Temperature had a significant effect on bug mortality (F 5

21,600; df 5 2, 21; P , 0.0001). Targeted heat treatment exposures for 15 min ateither 50 or 60uC resulted in 100% mortality of the adults tested, regardless oflocation in the vehicle. Heat treatments at 40uC resulted in very low mortality ofadults. All H. halys held under ambient conditions during this study resulted in0% mortality.

a. b.

Fig. 1. (a) Vehicle used for experiments parked inside a container heat treatmentfacility constructed by Willenius Wilhelmsen Logistics (WWL), and (b) the500,000 BTU propane heaters used to generate lethal temperatureextremes greater than 60uC for heat treatment of vehicles.

AIGNER & KUHAR: Lethal High Temperature Extremes 3

Fig. 2. Dead brown marmorated stink bugs in a mesh bag after removal fromunder the seat of a vehicle exposed to heat treatments at the Port ofSavannah, GA.

Table 2. Targeted temperatures, actual measured temperatures, andobserved mortality of H. halys adults after 15 min exposures toheat treatments applied to a vehicles at the Port of Georgia,Savannah, GA in 2015.

Actual measured temp.(mean uC 6 SE)

% mortality(mean 6 SE)a

Targettemp. (uC)

Under driver’sseat

Enginecompartment

Under driver’sseatb

Enginecompartmentb

40 39.1 6 0.2 42.2 6 0.3 2.5 6 2.5 b 17.5 6 17.5 b50 50.9 6 0.1 54.2 6 0.1 100.0 6 0.0 a 100.0 6 0.0 a60 65.0 6 0.7 67.1 6 0.8 100.0 6 0.0 a 100.0 6 0.0 a

aObserved for 24 h after 15 min of exposure to temperatures.bMeans within columnsfollowed bythe sameletter are not significantly different (ANOVA, LSD test,a 5 0.05).

4 J. Agric. Urban Entomol. Vol. 32 (2016)

Most insects cannot survive exposure to extreme heat (.50uC) for even briefdurations (Hammond 2015). High temperatures disrupt the function of proteins,

metabolic enzymes, and the respiratory and endocrine systems, all of which can

lead to insect mortality (Neven 2000). Our results showed that H. halys adults

are killed after exposure for 15 min to 50uC or 1 h or more exposure to 45uC.

These lethal high temperature levels are consistent with many other insects

(Hammond 2015). According to Burkes et al. (2000) and Fields & White (2002),

most stored-product insect pests (coleopterans and lepidopterans) are effectively

controlled under the following time-temperature combinations: 24 h at 40uC, 12 h

at 45uC, 5 min at 50uC, 1 min at 55uC, and 30 s at 60uC. Thus, H. halys appear to

follow a similar pattern of mortality.

These results may have implications on heat treatment control guidelines(restrictions) for shipping cargo. For instance, recent restrictions were placed on

the shipping of potential H. halys-infested cargo from the U.S. to other countries.

During periods of restriction, if vehicles cannot be fumigated prior to transport,

they are currently required to be heat-treated at 60uC for 20 min (restrictions set

by New Zealand) (Thompson 2014) or 30 min (restrictions set by Australia)

(Australian Government 2015) prior to boarding cargo ships. This heat treatment

regime has been found to be quite difficult to achieve in an efficient manner for

treating large cargo such as multiple vehicles because of the difficulty in

constantly maintaining an enclosure at 60uC. Consequently, fumigants have been

the primary choice for treatment of stink bugs in export goods mostly because of

efficiency (Thompson 2014). However, heat treatments are often less expensive,

and do not involve the use of toxic gases, such as phosphine (PH3) or methyl

bromide, which have numerous environmental and human safety issues

(Hammond 2015). Based on our research, heat treating export cargo at 50uCrather than 60uC would dramatically improve the efficiency of the process

without losing insect control efficacy. Based on our estimates and field testing

with WWL at the shipping port in Savannah, GA, such a switch would basically

cut the time of heat treatment in half, and thus double the amount of vehicles

that could be treated in a day. More efficient heat treatment controls could help to

reduce our reliance on fumigation as a means of insect control in exports.

Acknowledgements

The authors would like to thank Ashley Lohr and Jamie Hogue for their invaluable

assistance with the implementation of this study. We would like to extend our thanks to

Craig Kessler of the Georgia Port Authority and Phil Hansen and Sean Lilly of Wallenius

Wilhelmsen Logistics for allowing the use of their facility and their hospitality. This project

was funded in part by the USDA-NIFA-SCRI Grant # 2011-51181-30937.

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